Thực hiện phép tính: ​\( \left( {\frac{5}{7} - \frac{7}{5}} \right) - \left[ {\frac{1}{2} - \left( { - \frac{2}{7} - \frac{1}{{10}}} \right)} \right]\)

* Hướng dẫn giải

 \(\begin{array}{*{20}{l}} {\left( {\frac{5}{7} - \frac{7}{5}} \right) - \left[ {\frac{1}{2} - \left( { - \frac{2}{7} - \frac{1}{{10}}} \right)} \right]}\\ { = - \frac{{24}}{{35}} - \left[ {\frac{1}{2} - \left( { - \frac{{27}}{{70}}} \right)} \right]}\\ { = - \frac{{24}}{{35}} - \frac{{31}}{{35}} = - \frac{{11}}{7}} \end{array}\)